Solvent injection method for removing blockages in slurry pipelines



Dec. 15, 1970 V, R KRUKA 3,547,496

' SOLVENT INJECTION METHOD FOR REMOVING BLOCKAGES IN SLURRY PIPELINES Filed Feb. 26, 1969 INVENTOR v. R. KRUKA Hl AT ORNE-IY l United States Patent O 3,547,496 SOLVENT INJECTION METHOD FOR REMOVING BLOCKAGES IN SLURRY PIPELINES Vitold R. Kruka, Houston, Tex., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Feb. 26, 1969, Ser. No. 802,616 Int. Cl. B65g 53/04 U.S. Cl. 302-66 4 Claims ABSTRACT OF THE DISCLOSURE Method for removing blockages in a shut-down slurry pipeline. A solvent capable of dissolving slurry solid phase material is injected into those portions of the pipeline rwhere plug formation by slumping and compacting of slurry solid phase material is likely to occur under the inuence of gravity.

The present invention relates to pipeline transport perations; and more particularly, to a method for dissolving a plug formed by the downward movement of slurry solids in an inclined portion of pipeline during a shu-tdown period.

Transportation by pipeline is a major and growing industry. With the use thereof formerly confined almost entirely to movement of water, gas and petroleum products, pipelines, with the advent of slurry transport, have become useful for long and short hauls of a wide variety of raw materials and finished products.

With respect to the pipeline transportation of materials in slurry form, problems arise when such materials are moved through pipelines inclined to go over a hill or down into a valley. At these locations, durin'g a planned or emergency line shutdown, the solids of the transported slurry may settle out vertically and subsequently slide down the inclined portion of the pipeline, thereby causing a compacted plug Iwhich may be very ditiicult to dislodge and move when line shutdown is terminated and transport activities are resumed.

These difficulties are most commonly avoided by laying solids-carrying or slurry pipelines so that they do not exceed a slope 0r angle of inclination below which slidinlg does not occur. Alternatively, the inclined pipeline sections are emptied at each shutdown. Obviously, these alternative prior art approaches are not always feasible or economical, especially in those situations where long and relatively steep slopes are encountered. Slopes of this nature are being encountered with increasing frequency as slurry pipeline operations are being extended to new relatively inaccessible mountainous areas in the United States and elsewhere.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an improved and economical method whereby a blockage in a shut-down pipeline is economically and eiiiciently removed before pipeline restart.

This and other objects have been attained in the present invention by providing a method for removing blockages in slurry pipelines, said blockages being formed by slumping and compacting of the slurry solid phase under the iniiuence of gravity. A solvent is introduced under high pressure into those portions of the pipeline where said blockage or plug formation is likely to occur. The solvent must be one which is chemically inert with respect to the slurry liquid phase, miscible with the liquid phase and capable of dissolving the plug-forming solid material at ordinary temperatures.

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DESCRIPTION OF THE DRAWING The above-noted and other objects of the present invention will be understood from the following description, taken with reference to the accompanying drawing. In describing the invention in detail, reference will be made to the drawing in which like reference numerals designate corresponding parts throughout several views in which:

FIG. 1 is a diagrammatic view illustrating a given length of slurry pipeline which has been modified in a manner such as to carry out the teachings of the present invention; and

FIG. 2 is an enlarged cross-sectional view in longitudinal projection illustrating a selected portion of the pipeline section of FIG. l.

Referring now to FIG. 1, a given length of slurry pipeline 11 is illustrated in the position assumed thereby as the pipeline proceeds to and from a valley formed between two hills or mountains 12 and 13. The terrain illustrated is typical of that encountered in pipeline laying activities, although it should be understood that the teachin'gs of the present invention may be carried out in any topographical configuration wherein a portion of slurry pipeline is inclined.

The transportation of slurries consisting of solid particles in a uid medium by use of pipelines similar to that disclosed in FIG. 1 is quite well known, and such expedient is finding increasing use, especially in those situations where the source of raw materials is relatively remote and inaccessible from the point of delivery, which may be a suitable processing plant, for example. In the disclosed arrangement, it may be assumed for purposes of illustration that the slurry material being transferred through pipeline 11 as by means of conventional pumps (not shown) is moving through the line in the direction indicated by the arrows. However, the teachings of the presnt invention are, of course, applicable regardless of the direction of ow of the slurry.

As long as a sufliciently high yiiow rate is maintained in the pipeline, the solid matter of the slurry will remain in suspension Within the pumped liquid, even when the solid matter has a higher specific gravity than the liquid. If, however, the ow is stopped for any reason, i.e., the pipeline is shut down, such solid matter will settle out of suspension if its specific gravity is higher than that of the liquid. In the situation where the line is horizontal or the slope of the line is insuflicient to cause sliding of the settled solids, no problem is created by such settling out. Under these conditions, a liquid-rich channel remains open at the top of the line which allows the settled material to be resuspended with a minimum of diiiiculty upon resumption of slurry flow.

A serious problem can exist when the pipeline must be inclined to go over a hill or down a valley, as illustrated, for example, in FIG. 1. At these locations, the settling of solids followed by their sliding down the slope during a protracted shutdown can result in a compacted plug of material difficult, if not impossible, to move or resuspend. In the illustrated pipeline configuration, such solids would slide downwardly into the valley formed between hills or mountains 12 and 13. The solid material would then compress under its own weight to form a plug in the valley in an obvious manner.

Such plug formation is removed in accordance with the teachings of the present invention as follows. A pipe 21 is illustrated in FIG. 1 as being tapped into pipeline 11 at a location where plug formation is likely to occur upon pipeline shutdown due to slumping and compacting of the slurry solid phase under the influence of gravity. In FIG. l, for example, such plug for-mation would most likely occur at the low point formed between hills 12 and 13.

Pipe 21 is connected at its other end to the outlet of a pump 22 which may be of any suitable commercially available type capable of pumping a solvent material at sufficiently high presures to overcome the pressure in the pipe 11. The inlet of pump 22 is connected by means of conduit 24 to a suitable source of solvent such as tank 2S.

Assuming that it is desired to resume slurry transport after a pipeline shutdown, pump 22 is actuated to pump solvent from tank 2S. The pumped solvent proceeds through pipe 21 and into the interior of pipeline 11 in the manner ilustrated in FIG. 2. 'Pumping continues until sutiicient quantities of the slurry solid phase material (indicated by reference numeral 27) are dissolved so as to enable any remaining plug material to be transported along the pipeline upon actuation of the pipeline pumps (not shown) without undue pipeline pressures being creaated.

As stated above, the solvent should be selected so that it will not react with the slurry liquid phase, be miscible with the liquid phase, and be capable of dissolving the solid phase material at ordinary temperatures. As an example, if the solid phase material is sulfur (rhombic) and the liquid phase is crude oil, the several solvents will be suitable. Among the better solvents are aqueous sodium hydroxide, liquid ammonia, and ammonium sulfide. Sulfur is soluble in the stated solvents such that, not considering the oil, approximately 25% by weight of the resulting solution will be sulfur. Finally, although only one inlet pipe for the solvent is shown in FIG. 1, it should be understood that a plurality of inlets may be provided for each general pipe location if desired.

I claim as my invention:

1. A method for removing a blockage in a shut-down slurry pipeline, said slurry comprising a liquid phase and a solid phase and said blockage comprising a plug formed by the slumping and eompacting of the slurry solid phase under the inuence of gravity, said method comprising: establishing a ow path between the interior of said pipeline and a source of solvent which is chemically inert with respect to said liquid phase and capable of dissolving said solid phase, said flow path communicating with the interior of said pipeline at a location along said pipeline where said plug forma tion is likely to occur; pumping said solvent from said source into said pipeline to dissolve at least a portion of said plug; and resuming the transport of said slurry through said pipeline.

2. The method according to claim 1 wherein said slurry solid phase is sulfur and said liquid phase is crude oil and wherein said solvent is aqueous sodium hydroxide.

3. A method according to claim 1 wherein said slurry solid phase is sulfur and said liquid phase is crude oil and wherein said solvent is liquid ammonia.

4. The method according to claim 1 wherein said slurry solid phase is sulfur and said liquid phase is crude oil and wherein said solvent is ammonium sulde.

References Cited UNITED STATES PATENTS 562,232 6/1896 Miller 302-14 3,338,635 8/1967 Koranda 302-16 3,381,83l 5/1968 Oka 302-14 ANDRES H. NIELSEN, Primary Examiner U.S. Cl. XR. 302-l4, 64 

